System, nozzle and method for coating elastic strands

ABSTRACT

A method of contact coating at least one elastic strand with an adhesive is disclosed. A first strand has a periphery with an upper surface. The first strand is moved in a machine direction relative to a contact nozzle, the adhesive is discharged from the contact nozzle into contact with the upper surface of the first strand, and pressurized air is discharged at the adhesive on the first strand to cause the adhesive to spread around the periphery of the first strand without blowing adhesive off the first strand.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/867,373, filed Sep. 28, 2015, and published as U.S. Patent App. Pub.No. 2016/0016189 on Jan. 21, 2016, which is a continuation of U.S.patent application Ser. No. 13/443,461, filed Apr. 10, 2012, and issuedas U.S. Pat. No. 9,168,554 on Oct. 27, 2015, which claims the priorityof U.S. Provisional Patent App. No. 61/474,129, filed Apr. 11, 2011, thedisclosures of which are incorporated by reference herein.

TECHNICAL FIELD

This invention generally relates to fluid dispensing systems, nozzles,and methods, for applying adhesive onto one or more strands of stretchedelastic material.

BACKGROUND

Liquid adhesive, such as temperature and/or pressure sensitive adhesive,is applied onto one or more stretched strands of elastic material or anonwoven substrate during the manufacture of disposable hygiene productssuch as diapers, adult incontinence products and feminine hygieneproducts to form various elastic structure which are part of the hygieneproduct. For example, in a diaper one or more stretched elastic strandsare bonded between the backsheet and top sheet around the leg opening sothat the diaper snugly fits around the baby's leg. This is commonlyreferred to as the leg elastic application. One or more stretchedelastic strands are also bonded to different areas of the diaper duringthe construction of the barrier leg cuff and waist band. Twomeasurements that are commonly used when evaluating the effectiveness ofthe bond between the stretched elastic strands and the nonwovensubstrates are creep resistance and force retraction. Creep resistanceis a measure of how well the ends of the elastic strands remain adheredin position with respect to nonwoven substrates. A high level of creepresistance is desirable because creep will cause a strand to decouplefrom the nonwoven substrate and contract, thereby removing theelasticity and sealing capabilities of the hygiene product. Forceretraction is a measure of how much the adhered elastic strand canretract when the tension on the strand is released. A high level offorce retraction is also desirable because a low level of forceretraction renders the elasticity of the elastic strand and the hygieneproduct inadequate for its desired purposes, including product comfortand sealing capability. The adhesive is applied to the one or morestretched elastic strands using a non-contact dispensing system or acontact dispensing system.

In the conventional non-contact dispensing system, the adhesive isdispensed as a continuous filament and moved in a controlled pattern byimpacting the filament with air. Different types of nozzles are used inconventional non-contact dispensing systems which result in differentcontrolled patterns for the adhesive filament. In one non-contactdispensing system using a spiral nozzle the adhesive filament is movedback and forth in a helical or spiral pattern while it is in the airprior to contacting the stretched elastic strand. The helical or spiralpattern of the adhesive filament has a component in the direction ofmotion of the stretched elastic strand and another component transverseto the direction of motion of the stretched elastic strand. CF® nozzles(also identified as Controlled Fiberization™ nozzles) and Sure Wrap®nozzles, available from Nordson Corporation of Westlake, Ohio, arespiral nozzles used to form such a helical pattern with an adhesivefilament.

In another non-contact dispensing system using a meltblowing nozzle, theadhesive filament is moved back and forth in an oscillating pattern suchas a sinusoidal or similar pattern while it is in the air prior tocontacting the stretched elastic strand. The oscillating pattern of theadhesive filament is in a plane perpendicular to the motion of thestretched elastic strand.

In non-contact dispensing systems using meltblowing nozzles or spiralnozzles, the adhesive filament must be carefully controlled to ensurethat the adhesive filament is dispensed onto the narrow elastic strandand to ensure that the adhesive filament sufficiently wraps around theelastic strand. In this regard, the plurality of air jets used to spiralthe adhesive filament in Controlled Fiberization™ and Sure Wrap® nozzlesare positioned and angled with a high degree of precision to causemovement of the adhesive filament. If one of the air orifices deliveringthe air jets is blocked by adhesive material or debris during operation,the overall air pattern is disrupted or unbalanced, which leads to anuncontrolled adhesive filament pattern. The uncontrolled adhesivefilament pattern causes an undesirable adhesive deposit onto the strandor away from the strand entirely. The adhesive filament in thesenon-contact dispensing systems must also exhibit a relatively highviscosity to be adequately controllable in flight. The Sure Wrap® nozzleoperates using hot melt adhesives with viscosity in the range of 10,000centipoises to 15,000 centipoises, and the Controlled Fiberization™nozzle operates using hot melt adhesives with viscosity in the range of4000 centipoises to 15,000 centipoises.

Yet another type of non-contact dispensing system uses an adhesivenozzle to extrude a bead of adhesive onto a stretched elastic strandthat rotates as it passes by the adhesive nozzle without the use of anyprocess air on the bead of adhesive. The stretched elastic strand isrotated about its axis and moved by a nip roller assembly upstream ofthe adhesive nozzle. As a result, the continuous filament of adhesive isdeposited in a generally spiral pattern along the length of thestretched elastic strand. However, this type of non-contact dispensingsystem may be impractical because it is difficult to predictably rotateor twist the elastic strand at high production line speeds. Despite theabove difficulties, non-contact dispensing systems are widely usedbecause the resulting application of adhesive to the stretched elasticstrands results in a high level of both creep resistance and forceretraction.

One type of contact dispensing system uses a slit coating nozzleincluding one or more grooves configured to be filled with extrudedadhesive. A stretched elastic strand moving through the grooves will besurrounded with the extruded adhesive in the corresponding groove.Consequently, the stretched elastic strand is coated as the strand movesthrough the grooves in the slit coating nozzle. Slit coating nozzles donot have the filament control difficulties discussed above because theadhesive is not discharged in an airborne filament. Contact dispensingsystems using these slit coating nozzles tend to have difficultiesadequately coating the bottom surface of the stretched elastic strand.If the bottom surface of the strand is not adequately coated, there ispoor bonding between the elastic strand and a nonwoven substrate, whichresults in a low level of creep resistance. In order to effectively coatthe bottom surface of the elastic strand, the flow rate of adhesive intothe groove is commonly increased to a substantial extent, which resultsin a relatively thick coating of adhesive. This thick coating ofadhesive effectively bonds the elastic strand to the substrate andimproves the creep resistance, but because the strand is so heavilycoated, its ability to retract is impeded and results in poor forceretraction. The amount of adhesive dispensed to form the thick coatingalso tends to undesirably drip off the elastic strand onto otherequipment, especially when the production line is stopped. However, acontact dispensing system using a slit coating nozzle to apply adhesiveto stretched elastic strands is highly repeatable and consistent.

There is a need, therefore, for a contact adhesive dispensing system,nozzle, and method that supplies optimal coating characteristics ofadhesive on an elastic strand, including a high level of creepresistance and a high level of force retraction.

SUMMARY

In one embodiment of the invention, a contact nozzle is configured tocontact coat at least one stretched elastic strand with an adhesive andthen discharge pressurized air towards the adhesive on the strand. Forexample, a first strand is moving in a machine direction and includes aperiphery with an upper surface. The contact nozzle includes a nozzlebody having a first slot for receiving the first strand. The contactnozzle also includes a first adhesive passage formed in the nozzle bodyand terminating at a first adhesive orifice communicating with the firstslot. The first adhesive orifice is adapted to be directed at the uppersurface of the first strand to deliver the adhesive into contact withthe upper surface of the first strand. The contact nozzle also includesa first air passage positioned proximate to the first adhesive passageand terminating at a first air orifice positioned downstream from thefirst adhesive orifice in the machine direction. The first air orificeis adapted to be directed toward the upper surface of the first strandand is adapted to discharge air at the adhesive in contact with thefirst strand, thereby causing the adhesive to spread around theperiphery of the first strand.

The air discharged from the first air orifice is a pressurized air flow.In addition to spreading the adhesive, this air flow also keeps thenozzle body clear from adhesive build-up which would eventually char andadversely affect the operation of the contact nozzle. Pressurized airflow may be used with any type of contact coating nozzle and process toachieve these benefits. The combination of a contact coating processwith the additional air discharge at the adhesive on the strandadvantageously provides a strand coated with adhesive alongsubstantially its entire periphery. It is believed that this processcauses the thickness of adhesive coating to vary along the length of thestrand to maintain elasticity of the strand. To this end, when thecoated strand is bonded to one or more nonwoven substrates, such as indiaper construction, the adhesive forms a bond between the substratesand the strand that exhibits desirable levels of creep resistance andforce retraction believed to be a result of the thickness irregularitiesin the adhesive coating. Furthermore, the first strand is coated withthe adhesive around the entire periphery without a risk of an adhesivefilament, such as in a non-contact dispensing process, beinguncontrolled when impacted with process air. Such an uncontrolledfilament could lead to adhesive deposit at undetermined or undesirablelocations, including off the elastic strand.

In one alternative or additional aspect, the first air passage is formedin the nozzle body. The nozzle body has a rear surface that intersectsthe first slot at an adhesive release edge. More specifically, the rearsurface and the first slot define an interior angle between each otherat the adhesive release edge in an upstream direction from the rearsurface, the interior angle being an acute angle. Air from the first airorifice is discharged along the rear surface to assist with release ofadhesive from the nozzle body at the adhesive release edge. In thisregard, the air discharged along the rear surface from the first airorifice is adapted to impact the adhesive on the first strand at anacute angle relative to the machine direction.

In another alternative or additional aspect, the contact nozzle includesa mounting surface on the nozzle body that is adapted to be coupled to amodule for supporting the nozzle body. The mounting surface includes anadhesive inlet configured to receive the adhesive from the module. Alongitudinal axis defined through the first adhesive orifice and atleast a portion of the first adhesive passage intersects the mountingsurface at an acute angle. The air discharged from the first air orificeimpacts the adhesive on the strand at an acute angle. The acute anglemay be in the range of about 50 degrees to about 80 degrees.

In another alternative or additional aspect, the nozzle also includes anair discharge control device operatively coupled to the first airpassage. The air discharge control device is operable to intermittentlyblock air flow through the first air passage and the first air orifice.In one example, the air discharge control device causes the air flow tobe non-continuous. In another example, the air discharge control devicecauses the air flow to be pulsed in a periodic manner. The air dischargecontrol device, for example, may be a mechanical device or an aircontrol solenoid valve selectively blocking air flow through the firstair passage.

In yet another alternative or additional aspect, the nozzle includes asecond slot formed in the nozzle body and spaced from the first slot ina lateral direction transverse to the machine direction. The second slotis configured to receive a second strand moving in the machinedirection. The contact nozzle also includes a second adhesive passageformed in the nozzle body and terminating at a second adhesive orificecommunicating with the second slot. The second adhesive orifice isadapted to be directed at an upper surface of the second strand todeliver the adhesive into contact with the upper surface of the secondstrand. The contact nozzle also includes a second air passageterminating at a second air orifice positioned downstream from thesecond adhesive orifice in the machine direction. The second air passageis adapted to be directed toward the upper surface of the second strandand adapted to discharge air at the adhesive in contact with the secondstrand to cause the adhesive to spread around a periphery of the secondstrand. It will be understood that any embodiment of the nozzle mayinclude more than two slots, air passages, and adhesive passages inother embodiments when coating more than two strands. In this regard,any embodiment of the nozzle may include repeated structural elementsenabling similar coating of any number of stretched elastic strands.

In another alternative or additional aspect, the nozzle includes anotherair passage positioned proximate to the first air passage and alsodirected at the first strand. Therefore, in this embodiment two airpassages may be angled with respect to each other so as to causespreading of the adhesive around opposing sides of the periphery of thefirst strand. Furthermore, two air passages per strand provideredundancy in case one of the air passages becomes blocked, as eitherair passage is operable to spread the adhesive around the first strand.For example, in the embodiment described above including first andsecond air passages for corresponding first and second elastic strands,the contact nozzle may also include a third air passage formed in thenozzle body and adapted to direct air at the first strand, and a fourthair passage formed in the nozzle body and adapted to direct air at thesecond strand. The two air passages per strand may be staggered alongthe machine direction such that air from each of these air passagesstrikes the first strand at different locations along the machinedirection. Alternatively, these two air passages may be collinear oraligned with each other in a plane perpendicular to the machinedirection such that air from each of these air passages strikes thefirst strand at about the same location along the machine direction.

In another alternative or additional aspect, the contact nozzle furtherincludes an expansion chamber formed in the nozzle body andcommunicating with the first adhesive orifice. The expansion chamber issized to enable die swell of the adhesive exiting the first adhesiveorifice. In these embodiments, the contact nozzle also includes a strandguide on the nozzle body. The strand guide is adapted to position thefirst strand relative to the expansion chamber. As described in furtherdetail below, the expansion chamber or the strand guide may be partiallyor wholly defined by the first slot in certain embodiments consistentwith the current invention. The strand guide may alternatively beseparate from and coupled to the nozzle body in some embodiments.

In yet another alternative aspect, the first air passage is located inan air supply line. The air supply line may be coupled to the nozzlebody in one embodiment, or in another embodiment, may be separate fromthe nozzle body and positioned downstream from the nozzle body in themachine direction. Once again, the contact nozzle in this aspectincludes a rear surface on the nozzle body intersecting the first slotat an adhesive release edge, the rear surface and the first slotdefining an acute angle at the adhesive release edge such that air fromthe air supply line impacts the adhesive at an acute angle from themachine direction. The acute angle may be in the range of about 50degrees to about 80 degrees.

In another embodiment of the invention, a contact nozzle for coating atleast one elastic strand includes a nozzle body having a first elongateadhesive chamber for receiving the first strand. The first elongateadhesive chamber includes a first chamber surface configured to face thestrand. The contact nozzle also includes a first adhesive passage formedin the nozzle body and terminating at a first adhesive orifice in thefirst chamber surface. The first adhesive orifice is adapted to bedirected at the upper surface of the first strand to deliver theadhesive into contact with the upper surface of the first strand. Thecontact nozzle also includes a first air passage positioned proximate tothe first adhesive passage and terminating at a first air orificepositioned downstream from the first adhesive orifice in the machinedirection. The first air orifice is adapted to be directed toward theupper surface of the first strand and is adapted to discharge air at theadhesive in contact with the first strand, thereby causing the adhesiveto spread around the periphery of the first strand. In addition tospreading the adhesive, this air flow also assists with release of theadhesive from the nozzle body and keeps the nozzle body clear fromadhesive build-up which would eventually char and adversely affect theoperation of the contact nozzle.

In one aspect, the contact nozzle further includes a strand guide thatmay be integral with or coupled to the nozzle body, the strand guidebeing adapted to position the first strand relative to the firstelongate adhesive chamber. To this end, the nozzle body may include arear surface such that the first elongate adhesive chamber extendsbetween the strand guide and the rear surface. In one example, thestrand guide is positioned relative to the first elongate adhesivechamber such that a gap between the first chamber surface and the uppersurface of the strand remains constant in thickness along the length ofthe first elongate adhesive chamber. In an alternative example, thestrand guide is positioned relative to the first elongate adhesivechamber such that the gap reduces in thickness along the length of thefirst elongate adhesive chamber. In each of these examples, the gapdefines an expansion chamber sized to enable die swell of the adhesiveexiting the first adhesive orifice. This die swell causes an initialspreading of the adhesive around the periphery of the strand as thestrand moves through the first elongate adhesive chamber.

In yet another embodiment of the invention, a contact nozzle for coatingat least one elastic strand includes a nozzle body having a front side,a rear side, and a first V-shaped notch for receiving the first strand.The first V-shaped notch extends between the front and rear sides of thenozzle body. The contact nozzle also includes a first adhesive passageformed in the nozzle body and terminating at a first adhesive orificecommunicating with the first V-shaped notch. The first adhesive orificeis adapted to be directed at the upper surface of the first strand todeliver the adhesive into contact with the upper surface of the firststrand. The contact nozzle also includes an expansion chamber formed inthe nozzle body and communicating with the first adhesive orifice. Theexpansion chamber is sized to enable die swell of the adhesive exitingthe first adhesive orifice. The contact nozzle also includes a first airpassage positioned proximate to the first adhesive passage andterminating at a first air orifice positioned downstream from the firstadhesive orifice in the machine direction. The first air orifice isadapted to be directed toward the upper surface of the first strand andis adapted to discharge air at the adhesive in contact with the firststrand, thereby causing the adhesive to spread around the periphery ofthe first strand. In addition to spreading the adhesive, this air flowalso assists with release of the adhesive from the nozzle body and keepsthe nozzle body clear from adhesive build-up which would eventually charand adversely affect the operation of the contact nozzle.

In one aspect, the adhesive is mechanically spread about the peripheryof the strand by the V-shaped notch. To this end, the V-shaped notch mayinclude first and second converging surfaces connected at a top edge anddefining an angle between the converging surfaces in the range of 60degrees to 90 degrees. The V-shaped notch extends both upstream anddownstream in the machine direction from the expansion chamber. Inaddition, the V-shaped notch defines a strand guide adapted to positionthe first strand relative to the expansion chamber.

In another aspect, the contact nozzle includes alignment pins coupled tothe front side of the nozzle body and located upstream in the machinedirection from the V-shaped notch. The alignment pins are adapted toprevent the first strand from exiting the V-shaped notch duringapplication of adhesive.

In another embodiment of the invention, an adhesive dispensing systemfor coating at least one elastic strand moving in a machine directionwith an adhesive includes a module configured to receive a supply ofadhesive. The adhesive dispensing system also includes a contact nozzlecoupled to the module. The contact nozzle includes a nozzle body with afirst slot for receiving a first strand. The contact nozzle alsoincludes a first adhesive passage formed in the nozzle body andterminating at a first adhesive orifice communicating with the firstslot. The first adhesive orifice is adapted to be directed at an uppersurface of the first strand to deliver the adhesive into contact withthe upper surface of the first strand. The adhesive dispensing systemalso includes a first air passage positioned proximate to the firstadhesive passage and terminating at a first air orifice positioneddownstream from the first adhesive orifice in the machine direction. Thefirst air orifice is adapted to be directed toward the upper surface ofthe first strand and adapted to discharge air at the adhesive in contactwith the first strand, causing the adhesive to spread around theperiphery of the first strand. In addition to spreading the adhesive,this air flow also assists with release of the adhesive from the nozzlebody and keeps the nozzle body clear from adhesive build-up which wouldeventually char and adversely affect the operation of the contactnozzle.

In one aspect, the first air passage is formed in the nozzle body. Thenozzle body may include an expansion chamber communicating with thefirst adhesive orifice and sized to enable die swell of the adhesiveexiting the first adhesive orifice. The contact nozzle may also includea strand guide that is integral with or coupled to the nozzle body forpositioning the first strand relative to the expansion chamber. In oneembodiment, the first slot includes an elongate adhesive chamber adaptedto receive the first strand. The elongate adhesive chamber extends fromthe strand guide to a rear surface of the nozzle body and includes afirst chamber surface including the adhesive orifice. The first chambersurface is spaced from the strand so as to define a gap that defines anexpansion chamber sized to enable die swell of the adhesive as theadhesive moves through the elongate adhesive chamber. In anotherembodiment, the first slot includes a V-shaped notch that defines thestrand guide extending between front and rear sides of the nozzle body.The V-shaped notch is defined by two converging surfaces that areconnected at a top edge which intersects the expansion chamber.

In yet another embodiment of the invention, a method of contact coatingat least one elastic strand with an adhesive includes moving a firststrand in a machine direction relative to a contact nozzle. The methodalso includes discharging the adhesive from the contact nozzle onto anupper surface of the first strand. Pressurized air is then discharged atthe adhesive on the first strand, causing the adhesive to spread aroundthe periphery of the strand. The pressurized air also assists withrelease of adhesive from the contact nozzle and keeps the nozzle bodyclear from adhesive build-up.

In one alternative or additional aspect, the air is discharged from anair orifice in the contact nozzle. The air is also discharged at anacute angle relative to the machine direction as measured between thedirection of air discharge and the first strand upstream of the air inthe machine direction. For example, the acute angle from the machinedirection may be in the range of about 50 degrees to about 80 degrees.Thus, the air intersects the first strand at the acute angle. A smalleracute angle may be chosen to make the air flow more parallel to thestrand movement, thereby enabling higher air pressures to be used suchas during start-up of the adhesive dispensing system.

In another alternative or additional aspect, multiple streams of air aredischarged toward the adhesive on the strand to cause the adhesive tospread around opposing sides of the periphery of the strand. Themultiple streams of air may be staggered in the machine direction suchthat the multiple streams of air strike the strand at differentlocations along the machine direction. Alternatively, the multiplestreams of air are aligned in a plane perpendicular to the machinedirection such that the multiple streams of air strike the strand atabout the same location along the machine direction.

In another alternative or additional aspect, the pressurized air isdischarged continuously at the adhesive in contact with the firststrand, causing substantially continuous spreading of the adhesivearound the first strand. Alternatively, the pressurized air isdischarged non-continuously at the adhesive in contact with the firststrand, causing substantially non-continuous spreading of the adhesivearound the first strand. In one example, this non-continuous spreadingmay be caused by periodic pulsing of the pressurized air. Regardless ofthe method of discharging air, the adhesive is spread around theperiphery of the first strand such that the adhesive defines thicknessirregularities along the length of the first strand.

In one aspect, the method includes moving the first strand through anelongate adhesive chamber in communication with the first adhesiveorifice and spreading the adhesive in contact with the upper surface ofthe first strand. The first strand may be moved through the elongateadhesive chamber so as to be generally parallel to a chamber surfaceincluding the first adhesive orifice. Alternatively, the first strandmay be moved through the elongate adhesive chamber so as to move closerto the chamber surface along the length of the elongate adhesivechamber. In another aspect, the method includes moving the first strandthrough a V-shaped notch formed on the contact nozzle. The V-shapednotch mechanically moves the adhesive on the strand to spread theadhesive about the periphery of the strand.

The various features of the embodiments described above may be combinedin any configuration as desired. For example, all embodiments of thenozzle are capable of coating more than one stretched elastic strand byduplicating the structural elements used to coat the first stretchedelastic strand. Various additional features and advantages of theinvention will become more apparent upon review of the followingdetailed description of the illustrative embodiments taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of one embodiment of a contact nozzlefor use with an adhesive dispensing system according to the currentinvention.

FIG. 2A is a schematic side view of another embodiment of an adhesivedispensing system in a nonwoven assembly process.

FIG. 2B is a rear side perspective view of the nozzle of FIG. 2A.

FIG. 2C is a rear side view of the nozzle of FIG. 2A, showing multipleair passages in phantom.

FIG. 2D is a detailed rear side view of the nozzle of FIG. 2A, showingthe adhesive chamber and access slot.

FIG. 3A is a side cross-sectional view of the nozzle of FIG. 2B alongline 3-3, illustrating internal flow passages for adhesive and air.

FIG. 3B is a detailed side cross-sectional view of the nozzle of FIG.3A, further illustrating the adhesive release edge of the nozzle body.

FIG. 3C is a side cross-sectional view of the nozzle similar to FIG. 3A,except that the strand is in an angled orientation relative to thenozzle body and the adhesive chamber.

FIG. 3D is a detailed side cross-sectional view of the nozzle of FIG.3C, further illustrating the adhesive release edge of the nozzle body.

FIG. 4 is a perspective cross-sectional view of the nozzle of FIG. 2Balong line 3-3, illustrating adhesive spreading onto the strand.

FIG. 5A is a rear side view of an alternative embodiment of a nozzle,showing multiple air passages in phantom.

FIG. 5B is a rear side view of another alternative embodiment of anozzle, showing multiple air passages in phantom.

FIG. 6 is a perspective partially exploded view of another embodiment ofa nozzle.

FIG. 7 is a side cross-sectional view of the nozzle of FIG. 6 along line7-7, illustrating internal flow paths for adhesive and air.

FIG. 8A is a detailed side cross-sectional view of the air dischargecontrol device of FIG. 7 in a first position.

FIG. 8B is a detailed side cross-sectional view of the air dischargecontrol device of FIG. 7 in a second position.

FIG. 9 is a perspective cross-sectional view of the nozzle of FIG. 6along line 7-7, illustrating adhesive spreading onto the strand withpulsed air.

FIG. 10 is a schematic side view of another embodiment of an adhesivedispensing system in a nonwoven assembly process.

FIG. 11 is a side cross-sectional view of the adhesive dispensing systemof FIG. 10, illustrating internal flow paths for adhesive and air.

FIG. 12 is a schematic side view of yet another embodiment of anadhesive dispensing system in a nonwoven assembly process.

FIG. 13 is a schematic side view of another alternative embodiment of anadhesive dispensing system in a nonwoven assembly process, the adhesivedispensing system including a V-notch nozzle.

FIG. 14A is a rear side perspective view of the V-notch nozzle of FIG.13.

FIG. 14B is a rear side view of the V-notch nozzle of FIG. 13, showingmultiple air passages in phantom.

FIG. 14C is a detailed rear side view of the V-notch nozzle of FIG. 13,showing the adhesive being applied within one of the notches.

FIG. 15A is a side cross-sectional view of the V-notch nozzle of FIG.14A along line 15-15, illustrating internal flow passages for adhesiveand air and one of the notches without adhesive or a strand locatedwithin the notch.

FIG. 15B is a bottom view of the V-notch nozzle of FIG. 15A, furtherillustrating the notch and an adhesive orifice communicating with thenotch.

FIG. 15C is a side cross-sectional view of the V-notch nozzle similar toFIG. 15A, with adhesive material being applied to a strand within thenotch.

FIG. 15D is a detailed side cross-sectional view of the V-notch nozzleof FIG. 15C, further illustrating the adhesive release edge of theV-notch nozzle.

DETAILED DESCRIPTION

FIG. 1 illustrates a contact nozzle 2 configured for use in an adhesivedispensing system according to the present invention. The contact nozzle2 receives a stretched elastic strand 12 and applies an adhesive 14 tothe elastic strand 12 by contact coating the elastic strand 12 as theelastic strand 12 moves in a machine direction as indicated by arrow 16.The contact nozzle 2 is illustrated in this figure as a generalizedcontact nozzle 2, and it will be appreciated that a contact nozzlehaving any form and any particular shape may be used in accordance withthe principles of the current invention. Pressurized air (hereinafter“air”) is then discharged at the adhesive 14 on the elastic strand 12 asshown by arrow 18 downstream (relative to the machine direction 16) fromthe application of the adhesive 14. Although the air flow is representedby an arrow 18 originating at the contact nozzle 2 in FIG. 1, it will beunderstood that the air may be discharged from a separate air supplyline or by some other method unrelated to the contact nozzle 2 in otherembodiments within the scope of the current invention. The air flowfurther moves or spreads the adhesive 14 around the strand 12, therebyresulting in different thicknesses of adhesive coating along the lengthof the strand 12. The air flow also assists the adhesive in releasingfrom the contact nozzle 2 and keeps the contact nozzle 2 clear fromadhesive build-up which would eventually char and adversely affect theoperation of the contact nozzle 2. The air is a pressurized air flowsuch that the effects of impacting the air and the adhesive 14 on thestrand 12 are in addition to any effects ambient environmental air mayhave on the adhesive 14 as the elastic strand 12 moves in the machinedirection 16. The combination of a contact coating process with theadditional air discharge at the adhesive 14 on the strand 12advantageously provides a strand 12 reliably coated with adhesive 14along substantially its entire periphery. It is believed that thisprocess causes the thickness of adhesive coating to vary along thelength of the strand 12 to maintain elasticity of the strand 12. In thisregard, the adhesive 14 forms a coating with a plurality of thickerportions 84 a, a plurality of thinner portions 84 b, and preferably aplurality of void portions 84 c where no adhesive 14 is on the strand12. When the coated strand is bonded to one or more nonwoven substrates,such as in diaper construction, the adhesive forms a bond between thesubstrates and the strand that exhibits desirable levels of creepresistance and force retraction.

FIGS. 2A-15D illustrate several embodiments of the adhesive dispensingsystem 10, 310, 410, 510 according to the present invention including amodule 15 coupled with a contact nozzle 19, 110, 312, 412, 512. Themodule 15 may be a Universal™ module obtained from Nordson Corporationof Westlake, Ohio. The Universal™ module is further described in U.S.Pat. No. 6,676,038 to Gressett Jr. et al. and U.S. Pat. No. 7,559,487 toGressett Jr. et al., the disclosures of which are hereby incorporated byreference herein. In each of these exemplary embodiments and consistentwith the generalized embodiment shown in FIG. 1, the contact nozzleapplies an adhesive to an elastic strand by dispensing adhesive from anorifice and contact coating the strand with the adhesive adjacent to theorifice. After the adhesive has been contacted with the elastic strand,air is discharged toward the adhesive on the strand. The operation ofeach embodiment is described in further detail below.

FIGS. 2A-4 further illustrate one embodiment of an adhesive dispensingsystem 10 including a contact nozzle 19 for coating a strand 12 with anadhesive 14. More particularly, the nozzle 19 is coating one or morestretched elastic strands 12 with a hot melt adhesive 14 so as to forman elasticized portion of a hygiene product such as a diaper or sanitarynapkin. The nozzle 19 applies hot melt adhesive 14 onto the elasticstrand 12 as the elastic strand 12 moves in a machine direction througha slot (not shown in FIG. 2A) as indicated by arrows 16. The nozzle 19then discharges pressurized air at the hot melt adhesive 14 as shown byarrows 18 to cause the hot melt adhesive 14 to spread around a periphery20 of the elastic strand 12. The nozzle 19 uses hot melt adhesive 14 ofa generally low viscosity because the air is discharged at the hot meltadhesive 14 only when the hot melt adhesive 14 is in contact with thestrand 12. Since the hot melt adhesive 14 is not dispensed into the airas a filament and impacted with process air to move in a controlledpattern, there is no risk of uncontrolled filaments and no need for highviscosity to maintain filament integrity. The elastic strand 12 thencontinues in the machine direction to first and second bonding reels 22a, 22 b that couple first and second nonwoven substrates 24 a, 24 b suchas top and bottom sheets of a typical diaper to the elastic strand 12 ina sandwich-like construction. The hot melt adhesive thus bonds thenonwoven substrates 24 a, 24 b and the elastic strand 12 to form anelasticized portion of a hygiene product. Although FIG. 2A illustratesthe first and second nonwoven substrates 24 a, 24 b are two differentsheets of material, the sandwich-like construction could alternativelybe formed by one sheet of nonwoven material folded onto itself aroundthe elastic strand 12 to form two substrate layers. Furthermore, thefirst bonding reel 22 a and second bonding reel 22 b may be staggered oraligned in the machine direction.

It will be understood that the use of directional terms such as upper,top, bottom, front, rear, and lateral in the following description isfor illustrative purposes only and does not limit the structure ormethods to any such orientation. Furthermore, the shape and size ofvarious components of the nozzle 19 described below may be modified inaccordance with the needs of the user without departing from the scopeof the invention.

The nozzle 19 is shown in further detail in FIGS. 2B through 3D. Thenozzle 19 includes a nozzle body 30 including an upper body portion 32and a lower body portion 34. The nozzle body 30 also includes a top side36, a bottom side 38, a front side 40 extending between the top andbottom sides 36, 38, and a rear side 42 extending between the top andbottom sides 36, 38. The top side 36 defines a mounting surface 36configured to abut the module 15. The upper body portion 32 is generallylonger along the machine direction than the lower body portion 34 fromthe front side 40 to the rear side 42, thereby giving the nozzle 19 atapered appearance from the top side 36 to the bottom side 38. Thus, theupper body portion 32 defines connection portions 44 along the frontside 40 and the rear side 42 for aligning the nozzle 19 with the module15. The nozzle 19 is clamped to the module 15 such that the top side 36(i.e., the mounting surface) is coupled to the module 15 as wellunderstood from U.S. Pat. Nos. 6,676,038 and 7,559,487. In someembodiments, the nozzle body 30 may have a different shape and size,including but not limited to being formed by stacked plates.

The nozzle 19 further includes an adhesive inlet 50 and an air inlet 52disposed along the mounting surface at the top side 36 of the nozzlebody 30. The adhesive inlet 50 is surrounded by a seal groove 54 thatreceives a seal member 56 between the nozzle 19 and thepreviously-described module 15. The adhesive inlet 50 is fluidicallycoupled to a plurality of adhesive passages 58 formed in the nozzle body30 and extending into the lower body portion 34 of the nozzle body 30.Although three adhesive passages 58 are shown in FIG. 2C, more or feweradhesive passages 58 may be coupled to the adhesive inlet 50 in otherembodiments of the nozzle 19. Each adhesive passage 58 is spaced fromadjacent adhesive passages 58 in a lateral direction transverse to themachine direction. Each adhesive passage 58 delivers adhesive 14 fromthe adhesive inlet 50 to an adhesive orifice 60 communicating with arespective slot 62 formed near the bottom side 38 of the nozzle body 30.The slot 62 of this embodiment includes an elongate adhesive chamber 62as described in further detail with reference to FIGS. 3A and 3B below.

In a similar manner, the air inlet 52 is fluidically coupled to aplurality of air passages 64 formed in the nozzle body 30 and extendinginto the lower body portion 34. Each air passage 64 is positionedproximate to and directly rearward of the respective adhesive passage 58within the nozzle body 30. In this regard, each set of adhesive passages58 and air passages 64 coats one strand 12 passing through the nozzle19. Furthermore, each set of adhesive passages 58 and air passages 64 inthe illustrated embodiment includes only one adhesive passage 58 andonly one air passage 64 for the corresponding strand 12. As shown inFIGS. 3A and 3B, it will be understood that at least a lower portion ofthe adhesive passage 58 and the air passage 64 are manufactured so as tobe generally parallel to one another, thereby avoiding interferencesbetween the passages 58, 64 within the nozzle body 30. In addition, itwill be understood that the adhesive passage 58 may be machined toinclude a slight bend at one point between the adhesive inlet 50 and theadhesive orifice 60 as shown in FIG. 3A or may be machined to follow alinear path between the adhesive inlet 50 and the adhesive orifice 60 inother embodiments (for example, FIG. 15A) without departing from thescope of the current invention. Each air passage 64 is spaced fromadjacent air passages 64 in the lateral direction. Each air passage 64delivers air from the air inlet 52 to an air orifice 66 directed at theadhesive 14 in contact with the strand 12. More particularly, the airorifice 66 is positioned adjacent to a rear surface 68, which is part ofthe rear side 42 of the nozzle body 30. As such, air discharged from theair passage 64 and the air orifice 66 is directed along the rear surface68 to act on the adhesive 14 as the strand 12 exits the adhesive chamber62. As shown in FIG. 2D and 3B, the air orifice 66 is located in anintermediate surface 69 extending from the rear surface 68. Thethicknesses 69a and 69b of the intermediate surface 69 on opposite sidesof the air orifice 66 are minimized so as to reduce any eddy currentsthat tend to form adjacent oblique surfaces surrounding the air orifice66. The reduction of eddy currents along the intermediate surface 69makes the delivery of air toward the strand 12 more laminar.

The nozzle 19 further includes one or more strand guides 70 positionedproximate to the nozzle body 30 for guiding the respective strands 12into the corresponding adhesive chambers 62. Strand guides used withspiral nozzles are further described in U.S. Pat. No. 7,647,885 to Craneet al. and U.S. Patent Publication No. 2010/0024997 to Saine et al.,which are assigned to Nordson Corporation and the disclosures of whichare hereby incorporated by reference herein. In the illustratedembodiment, each strand guide 70 is coupled to the nozzle body 30 andincludes a guide slot 72 in communication with the correspondingadhesive chamber 62. The guide slot 72 tapers inwardly in the machinedirection so that the strand 12 is accurately positioned in the adhesivechamber 62 to travel underneath the adhesive orifice 60 and the airorifice 66. Each strand guide 70 also defines a lateral width W₁ asshown in FIG. 2C. Thus, the adjacent sets of adhesive passages 58 andair passages 64 in the nozzle body 30 are spaced laterally from oneanother by any distance above a minimum spacing defined by the lateralwidth W₁ of the strand guides 70. In this regard, the provision of onlyone air passage 64 and only one adhesive passage 58 per strand 12requires less width in the nozzle body 30 than the lateral width W₁ ofthe strand guides 70. For at least this reason, the minimum spacingbetween multiple strands 12 running through the nozzle 19 is dependentupon the strand guides 70 rather than the adhesive passage 58 and airpassage 64.

In one example, each strand guide 70 is separately formed and insertedinto a corresponding guide cavity 74 in the nozzle body 30 as shown inthe figures. In this arrangement, the strand guides 70 are replaceableif the moving strand 12 wears out the guide slot 72. Furthermore, thestrand guides 70 in this arrangement are formed from stainless steelwith a Titanium Nitride coating for resisting frictional wear, while thenozzle body 30 is machined from a different material such as aluminum orbrass. The strand guides 70 can include only the guide slot 72 as shownor can be modified to include the guide slot 72 and the adhesive chamber62 in another non-illustrated embodiment. To this end, the strand guide70 of the illustrated embodiment is formed separately and locatedupstream from the adhesive chamber 62. In other embodiments, the strandguides 70 are formed integrally with the nozzle body 30. In thisarrangement, the nozzle body 30 may be machined from steel and aTitanium Nitride coating may be used in the area of the integral strandguide 70 to resist frictional wear. In still another arrangement, thestrand guides 70 are coupled to the nozzle body 30 or coupled to anotherstructure adjacent the nozzle body 30 such as a module that carries thenozzle 19.

FIGS. 2D, 3A, and 3B further illustrate one of the elongate adhesivechambers 62 (e.g., the slots 62) in greater detail. The adhesive chamber62 includes a chamber surface 76 on the nozzle body 30, the chambersurface 76 including the adhesive orifice 60 communicating with theadhesive passage 58. The nozzle body 30 further includes an access slot77 extending downwardly from the adhesive chamber 62 to the bottom side38 as shown in FIG. 2D. The access slot 77 communicates with theadhesive chamber 62 and the guide slot 72 in the strand guide 70 so thatthe elastic strand 12 may be inserted upwardly through the access slot77 into the guide slot 72 and the adhesive chamber 62 rather than beingthreaded through those elements. The adhesive chamber 62 is shown as aslot in FIGS. 3A and 3B, but it will be understood that the adhesivechamber 62 may define different shapes and sizes in other embodiments,including being tapered. In embodiments with a tapered adhesive chamber62, the taper is continuous or stepped. Furthermore, while the adhesivechamber 62 and the access slot 77 are milled into the nozzle body 30 inthe illustrated embodiment, alternative embodiments of the nozzle 19 mayinclude an adhesive chamber 62 formed by one or more apertures drilledthrough the nozzle body 30 along the machine direction. An access slot77 may then be milled between the drilled apertures and the bottom side38 of the nozzle body 30. In one example, an adhesive chamber 62including two drilled apertures defines a figure-8 cross-sectionalshape, and the access slot 77 may be milled into the intersection of thetwo drilled apertures.

Thus, the adhesive chamber 62 is in fluid communication with theadhesive passage 58 through the adhesive orifice 60. The guide slot 72of the strand guide 70 positions the strand 12 within the adhesivechamber 62 so as to define a gap 78 between the chamber surface 76 andan upper surface 80 of the strand 12. The gap 78 defines an expansionchamber that is sized to permit an initial expansion of adhesive 14 intothe adhesive chamber 62 above the strand 12 due to the effects of dieswell within the adhesive chamber 62. In the exemplary embodiment shown,the gap 78 is sized within the range of about 0.005 inches to about0.015 inches. As well understood in the art, die swell refers to thephenomenon of a stream of material swelling in volume after beingcompressed in a narrow die or passage (such as the adhesive passage 58).The adhesive chamber 62 is substantially filled with adhesive 14 at thegap 78 such that the adhesive 14 is applied to the elastic strand 12 asthe strand 12 moves through the adhesive chamber 62. Thus, the adhesivechamber 62 is configured to encourage initial expansion and spreading ofthe adhesive 14 in this embodiment. Because the elastic strand 12 passesthrough the adhesive chamber 62 at a greater velocity than the adhesive14 is supplied to the adhesive chamber 62, the strand 12 draws theadhesive 14 from the adhesive chamber 62 in a manner that ensures thatthe strand 12 is not coated with unnecessary or excess adhesive 14.Additionally, the gap 78 between the chamber surface 76 and the uppersurface 80 of the strand 12 in combination with the effects of die swellcauses the adhesive 14 to begin spreading around the periphery 20 of thestrand 12 as the strand 12 passes through the adhesive chamber 62 asindicated in phantom in FIG. 3B.

As shown in FIG. 2D, the rear surface 68 of the nozzle body 30 alsointersects a lower rear surface 81 at an elongate edge 82. The adhesivechamber 62 and the access slot 77 terminate at the lower rear surface81. The elongate edge 82 includes an adhesive release edge 82 a wherethe chamber surface 76 intersects the rear surface 68. The chambersurface 76 and the rear surface 68 define an interior angle α (FIG. 3B)between the surfaces 76 and 68 at the adhesive release edge 82 a. Theinterior angle a is an acute angle so that the adhesive release edge 82promotes sharp release of the adhesive 14 on the strand 12 from thenozzle body 30. The interior angle α is measured in an upstreamdirection along the machine direction from the adhesive release edge 82a. To this end, the interior angle α is defined by the nozzle body 30 atthe adhesive release edge 82 a. In the illustrated embodiment, the acuteangle from the machine direction may be in the range of about 50 degreesto about 80 degrees. As the acute angle α is made smaller within thisrange (such as the relatively small acute angle α shown in FIG. 3B), theair flow from the air orifice 66 becomes more parallel to the movementof the strand 12 along the machine direction, which enables higher airpressures to be used for the air flow to spread the adhesive 14 withoutblowing the adhesive 14 off of the strand 12. The adhesive release edge82 a applies a wiping or spreading effect on the adhesive 14 withoutcontacting the strand 12. This spreading effect increases as the strand12 is positioned closer to the adhesive release edge 82 a.

The air discharged from the air orifice 66 along the rear surface 68 asshown by arrows 18 also assists with release of adhesive 14 from thenozzle body 30 at the adhesive release edge 82 a. The air travelingalong the rear surface 68 strikes the upper surface 80 of the strand 12at a non-perpendicular angle such that the formation of any eddycurrents around the adhesive release edge 82 a is believed to bediscouraged. More specifically, the air strikes the upper surface 80 ofthe strand 12 at the acute angle α described above. Therefore, theadhesive 14 remains attached to the moving strand 12 downstream of theadhesive chamber 62 rather than building up on the nozzle body 30. As aresult, the risk of adhesive 14 building up on the nozzle body 30 andblocking the air orifice 66 is substantially reduced or eliminated.

In the illustrated embodiment, the width of the strand 12 in a stretchedcondition is about 0.008 inches to 0.02 inches. The adhesive orifice 60has a diameter of about 0.024 inches so that the adhesive 14 applied tothe strand 12 begins spreading around the periphery 20 of the strand 12immediately upon application in the adhesive chamber 62. The air orifice66 has a diameter of about 0.02 inches in the illustrated embodiment.The pressure of air discharged through the air orifice 66 is set so thatthe air orifice 66 discharges approximately 0.15 to 0.50 cubic feet ofair per minute. When only one air orifice 66 is used to dischargeprocess air at each strand 12, the overall use of process air and thecorresponding infrastructure necessary to provide the process air isreduced.

In another arrangement shown in FIGS. 3C and 3D, the nozzle body 30 hasbeen moved downward with respect to the strand 12 such that the strand12 angles upwardly on either side of the guide slot 72 and passesthrough the adhesive chamber 62 at an angle with respect to the chambersurface 76. To this end, the strand 12 moves within the adhesive chamber62 so as to be closer to the chamber surface 76 at the exit of theadhesive chamber 62 that at the guide slot 72. In this orientation, thegap 78 a between the chamber surface 76 and the upper surface 80 of thestrand 12 narrows along the length of the adhesive chamber 62 such thatan exit gap 78 b at the exit of the adhesive chamber 62 is narrowed fromthe gap 78 a. This narrowed exit gap 78 b increases the amount of timethat the adhesive 14 is located in the adhesive chamber 62, therebycausing increased spreading of the adhesive 14 around the periphery 20of the strand 12 within the adhesive chamber 62 due to the effects ofdie swell. Once again, the gap 78 a is sized within the range of about0.005 inches to about 0.015 inches. The adhesive release edge 82 a alsoapplies a greater spreading effect on the adhesive 14 as a result of thenarrowed exit gap 78 b at the exit of the adhesive chamber 62.Therefore, the adhesive 14 is forced to begin spreading around theperiphery 20 of the strand 12 before the strand 12 exits the adhesivechamber 62 and the nozzle body 30. It will be understood that thenarrowing of the gap 78 a along the length of the adhesive chamber 62may be achieved in other manners while keeping the strand 12 generallyhorizontal, including but not limited to tapering the adhesive chamber62.

The operation of the nozzle 19 is shown in FIGS. 3A-3D and 4. Theadhesive passage 58 delivers the adhesive 14 through the adhesiveorifice 60 to fill the adhesive chamber 62. The adhesive 14 is appliedto the upper surface 80 of the strand 12 in the illustrated embodiment.The strand 12 then draws the adhesive 14 through the adhesive chamber 62until the strand 12 emerges from the rear side 42 of the nozzle body 30.At this rear side 42, a portion of the adhesive 14 releases from thenozzle body 30 by virtue of the air moving along the rear surface 68 andthe adhesive release edge 82 a.

Upon release from the nozzle body 30, the adhesive 14 in contact withthe strand is struck by additional air discharged from the air orifice66 toward the elastic strand 12. The air causes the adhesive 14, whichis only partially spread around the periphery 20 of the strand 12, tospread more around the periphery 20 of the strand 12 in order to coatthe strand 12 with the adhesive 14. The air discharged from the airorifice 66 does not blow the adhesive 14 off of the strand 12 becausethe adhesive 14 is applied to the strand 12 and begins forming anadhesive bond with the strand 12 prior to being struck with the air.Additionally, the adhesive 14 coats substantially the entire periphery20 of the strand 12 as explained below instead of wrapping a filamentrandomly around portions of the periphery 20.

The adhesive 14 forms a coating on the strand 12 that appears continuousto the naked eye, but it is believed that this coating is not entirelycontinuous along the length of the strand 12. As described above, theadhesive 14 is extruded from the adhesive orifice 60 into the adhesivechamber 62. The stretched elastic strand 12 is received in the adhesivechamber 62 as the strand 12 moves in the machine direction.Consequently, the adhesive 14 contacts the moving strand 12 and rapidlyaccelerates to be released from the nozzle 19 at the adhesive releaseedge 82 a. The rapid acceleration of the adhesive 14 causes the adhesive14 to be applied to the strand 12 in a semi-starved state, such that theamount of adhesive 14 varies along the length of the strand 12. It isbelieved, more particularly, that the adhesive 14 forms localized massesseparated by thinner sections that preferably may break as the adhesive14 is accelerated by the elastic strand 12. As a result, the adhesive 14forms a coating with a plurality of thicker portions 84 a, a pluralityof thinner portions 84 b, and preferably a plurality of void portions 84c where no adhesive 14 is on the strand 12. The localized masses ofadhesive 14 are configured to become discrete bond points when securingthe elastic strand 12 to one or both of the nonwoven substrates 24 a, 24b. Then the adhesive 14 is struck with air from the air orifice 66,which causes spreading of the adhesive 14 that tends to further breakthe adhesive 14 into localized masses.

As a result of these operational steps, the resultant coating formed onthe strand 12 is believed to include thickness irregularities along thelength of the strand 12. In this regard, FIGS. 3B and 3D schematicallyillustrate that the adhesive 14 forms a coating with a plurality ofthicker portions 84 a, a plurality of thinner portions 84 b, andpreferably a plurality of void portions 84 c where no adhesive 14 is onthe strand 12. These portions 84 a, 84 b, 84 c are shown as an artist'srendering and it will be appreciated that the actual appearance anddistribution of these portions 84 a, 84 b, 84 c may vary in actual usedepending on operation parameters such as air pressure. The repeatablecontinuous appearance to the naked eye of the adhesive 14 on the strand12 is desirable in hygiene products, but the thickness irregularities ofthe coating believed to be formed by the adhesive 14 advantageouslyresults in the thicker portions 84 a functioning as discrete bond pointsformed along the length of the strand 12 when adhered to one or more ofthe substrates 24 a, 24 b, as described in detail above. Morespecifically, when bonded between two nonwoven substrates 24 a, 24 b,the coated elastic strand 12 is coated with sufficient adhesive 14 toexhibit a high level of creep resistance and, by virtue of the discretebond point effect, also exhibits a high level of force retraction.

In the exemplary coating operation described above in connection withthe nozzle 19, the hot melt adhesive 14 used to coat the elastic strand12 has a viscosity in the range of about 3,000 to about 12,000centipoises and possibly higher depending on various operatingparameters such as the air pressure. The lower viscosity of the adhesive14 leads to improved bonding with a nonwoven substrate and improvedpenetration into the nonwoven substrate 24 a, 24 b. Furthermore, thenozzle 19 of the present invention can operate with a wide range ofviscosities because of this broad potential adhesive viscosity range.The lower viscosity of the hot melt adhesive 14 also allows for theadhesive 14 to be applied at a higher temperature to the strand 12 andalso reduces overall consumption of adhesive material to coat the strand12. For example, the amount of hot melt adhesive 14 applied to thestrand 12 is in the range of about 25 mg/meter to about 120 mg/meter.The higher application temperatures lead to better adhesive bonds beingformed with the nonwoven substrate 24, even with less adhesive 14consumption. Consequently, the nozzle 19 significantly reduces the costsof assembling hygiene products by reducing the amount of adhesive 14 andprocess air consumed and operating with lower adhesive viscosity.

In some alternative embodiments, the nozzle 19 includes an adhesivepassage 58, multiple air passages 64, and multiple air orifices 66 foreach strand 12. As shown in FIGS. 5A and 5B, the nozzle 19 includes afirst air passage 64 a and first air orifice 66 a directed toward oneside of the strand 12, and the nozzle 19 also includes a second airpassage 64 b and second air orifice 66 b directed toward the oppositeside of the strand 12. In one alternative shown in FIG. 5A, the firstair passage 64 a is staggered in the machine direction from the secondair passage 64 b such that the air flow from each air passage 64 a, 64 bstrikes the adhesive 14 on the strand 12 in sequence. In anotheralternative shown in FIG. 5B, the first and second air passages 64 a, 64b are aligned collinear and within a plane oriented perpendicular to themachine direction such that the air flow from each air passage 64 a, 64b strikes the adhesive 14 on the strand 12 at about the same location.It will be understood that the number and orientation of the airpassages 64 and air orifices 66 may be modified in other embodimentswithout departing from the scope of the invention. Furthermore, it willbe understood that each air passage 64 a, 64 b continues to dischargeair at an acute angle with respect to the machine direction to possiblydiscourage the formation of eddy currents. The first and second airpassages 64 a, 64 b provide redundancy in case one of the air passages64 a, 64 b becomes blocked, as either air passage 64 a, 64 b is capableof spreading the adhesive 14 around the strand 12. However, theprovision of two or more air passages 64 can result in improved adhesivespreading.

Another embodiment of a contact nozzle 110 is illustrated in FIGS. 6-9.The nozzle 110 of this embodiment includes substantially all of theelements previously described with reference to the embodiment of FIGS.2A-4, and these elements are repeated in FIGS. 6-9 with the samereference numbers as the previous embodiment. These elements and theadvantageous operation of the nozzle 110 is not repeated in detail, asthe following discussion focuses on the differences in this embodiment.

As shown in FIGS. 6 and 7, the nozzle 110 of this embodiment furtherincludes an air discharge control device 190 operatively coupled to theair passage 64 in the nozzle body 30. The air discharge control device190 intermittently blocks pressurized air discharged from the airorifice 66. More particularly, the air discharge control device 190 ofthe illustrated embodiment includes an elongate rotatable member 192positioned in a lateral aperture 194 through the nozzle body 30. Therotatable member 192 intermittently blocks air flow through the airpassage 64. To this end, the rotatable member 192 includes a pluralityof fins 196 that are rotated to intermittently block air flow throughthe air passage 64. As shown in FIG. 7 by arrows 198, the rotatablemember 192 rotates the fins 196 in the air passage 64 to effectivelydivide a continuous air flow in the air inlet 52 into pulses of air flowat the air orifice 66. Consequently, the second coating nozzle 110 isoperable to discharge pulses of air at the adhesive 14 on the elasticstrand 12. It will be understood that the rotatable member 192 could beremoved from the lateral aperture 194 to permit continuous air flowthrough the air passage 64 in other operations. Alternatively, the airdischarge control device 190 includes an air control solenoid valve thatselectively blocks air flow through the air passage 64 to form acontinuous flow or a pulsed flow of air.

The rotatable member 192 includes lateral ends 200 engaged with endbearings 202 inserted into opposing sides of the lateral aperture 194.The end bearings 202 are held in position by locking pins 204 insertedthrough vertical apertures 206 in the nozzle body 30. More specifically,the locking pins 204 engage reduced-diameter portions 208 of the endbearings 202 to prevent movement of the end bearings 202 and therotatable member 192 in the lateral direction out of the lateralaperture 194. It will be understood that the rotatable member 192alternatively includes flow passages that intermittently come intocommunication with the air passage 64 rather than fins 196 in someembodiments. Furthermore in other embodiments, the rotatable member 192is replaced by alternative structure operable to control air flowthrough the air passage 64.

FIGS. 8A and 8B further illustrate the operation of the rotatable member192 of the illustrated embodiment. The lateral aperture 194 divides theair passage 64 into an upper passage portion 64 x leading to the airinlet 52 and a lower passage portion 64 y leading to the air orifice 66.Each of the fins 196 defines an outer surface or land 222 thatintermittently rotates into engagement with a wall portion 224 of thelateral aperture 194 extending between the upper and lower passageportions 64 x, 64 y. In the position shown in FIG. 8A, the land 222 ofone of the fins 196 engages the wall portion 224 to effectively blockpassage of air from the upper passage portion 64 x to the lower passageportion 64 y. When the rotatable member 192 moves to the position shownin FIG. 8B, none of the lands 222 of the fins 196 are engaged with thewall portion 224 such that air may flow from the upper passage portion64 x to the lower passage portion 64 y. Thus, as the rotatable member192 rotates, the air flow through the air passage 64 and the air orifice66 is pulsed.

The rotatable member 192 is automatically driven by the pressure of theair flow or is separately driven, such as by an external motor (notshown). Thus, the frequency and length of the air pulses is controlledto any desired configuration. For example, the number and shape of fins196 may be modified on the rotatable member 192 to modify the pulsedpattern of the air flow. The air discharge control device 190 isoperable to produce any particular type of pulsed air discharge to meetthe requirements of the user. The pulsing of the air flow may be betweenany two or more flow rates, one of which may be zero such as when thefins 196 completely block air flow through the air passage 64. When theair discharge is pulsed at regular intervals by the air dischargecontrol device 190, the adhesive 14 is spread at regular intervals asshown in FIG. 9. In this regard, the strand 12 includes first portions212 downstream of the nozzle 110 where the adhesive 14 is completelyspread around the periphery 20 of the strand 12 and second portions 214downstream of the nozzle 110 where the adhesive 14 remains onlypartially spread around the periphery 20 of the strand 12. In such anoperation, the thicker amounts of adhesive 14 remaining on the uppersurface 80 of the strand 12 at the second portions 214 form a discretebond point effect when the strand 12 is coupled to the nonwovensubstrate 24 at the bonding reel 22. This discrete bond effect is alsoenhanced by any thickness irregularity of the coating of adhesive 14along the length of the strand 12 previously described with reference tothe previous embodiment of FIGS. 2A-4. Also described above, thisdiscrete bond point effect is advantageous because the elastic strand 12when bonded between two nonwoven substrates 24 a, 24 b exhibits a highlevel of force retraction as well as a high level of creep resistance.Although the second portions 214 of the strand 12 are shown at aparticular spacing in FIGS. 6-9, it will be appreciated that the spacingbetween these second portions 214 may be increased or reduced in otherembodiments. It will also be understood that while the acute angle α isshown as a larger angle in this embodiment than in the embodiment shownin FIGS. 2A-4, the acute angle α still remains within the desired rangeof about 50 degrees to about 80 degrees for the reasons described indetail above.

Just like the previously described embodiment, the nozzle 110significantly reduces the costs of assembling hygiene products byreducing the amount of adhesive 14 consumed and operating with loweradhesive viscosity. Thus, the nozzle 110 enables more reliable andeconomical coating of elastic strands 12.

An alternative embodiment of an adhesive dispensing system 310 for usein a hygiene product assembly process is shown in FIGS. 10 and 11. Theadhesive dispensing system 310 includes a contact nozzle 312 includingmany of the same elements as the previously-described nozzles 19, 110.To this end, the same elements from the previous embodiments arenumbered with the same reference numbers in this embodiment. The nozzle312 again includes an adhesive passage 58 and an adhesive orifice 60adapted to direct adhesive 14 to fill an adhesive chamber 62 (e.g., aslot 62) and be dispensed onto a moving elastic strand 12 in theadhesive chamber 62. The nozzle 312 of this embodiment does not includeair passages or air orifices formed in the nozzle 312.

Instead, the adhesive dispensing system 310 further includes an airsupply line 314. The air supply line 314 includes an air passage (notshown) and terminates in an air orifice 316 directed at the uppersurface 80 of the strand 12. Thus, the air supply line 314 and airorifice 316 operate to discharge pressurized air at the strand 12,causing spreading of the adhesive 14 on the strand 12 as previouslydescribed in other embodiments. As shown in FIG. 11, the air supply line314 is coupled to a slot 318 in the nozzle 312 so that the air supplyline 314 is positioned proximate to the nozzle 312. In otherembodiments, the air supply line 314 is held proximate the nozzle 312 byother known mounting devices and methods such as by the module 15. Inthe embodiment of FIGS. 10 and 11, the air orifice 316 discharges airalong a rear surface 68 of the nozzle 312 so as to assist in releasingthe adhesive 14 from the nozzle 312 at an adhesive release edge 82 a.

Consequently, the adhesive dispensing system 310 of this embodimentoperates similarly as the nozzles 19, 110 previously described. Morespecifically, the adhesive dispensing system 310 spreads the adhesive 14on the elastic strand 12 in a substantially continuous manner or apulsed manner. The adhesive dispensing system 310 can advantageouslycoat a strand 12 with adhesive 14 with low adhesive 14 consumption and alow adhesive viscosity, if desired. The adhesive dispensing system 310is positioned to coat the strand 12 before the strand 12 travels to thepreviously described bonding reels 22 a, 22 b downstream from the airsupply line 314 for coupling one or more nonwoven substrates 24 a, 24 bto the coated strand 12. Therefore, the adhesive dispensing system 310improves the hygiene product assembly process.

Yet another alternative embodiment of an adhesive dispensing system 410for use in a hygiene product assembly process is shown in FIG. 12.Similar to the previously described adhesive dispensing system 310, thisembodiment of the adhesive dispensing system 410 includes a contactnozzle 412 and an air supply line 414 positioned downstream from butproximate to the nozzle 412 in the machine direction. More particularly,the air supply line 414 is positioned to be spaced from the nozzle 412so that the adhesive 14 is partially spread around the periphery 20 ofthe strand 12 prior to being impacted by pressurized air from the airsupply line 414. In all other respects, the adhesive dispensing system410 operates in the same manner as the previously described nozzles 19,110 and system 310. Therefore, the adhesive dispensing system 410 ispositioned to coat the elastic strand 12 before the strand 12 travels tothe previously described bonding reels 22 a, 22 b downstream from theair supply line 414 for coupling one or more nonwoven substrates 24 a,24 b to the coated strand 12. For all of the same reasons described indetail above, the adhesive dispensing system 410 improves the hygieneproduct assembly process.

An alternative embodiment of an adhesive dispensing system 510 for usein a hygiene product assembly process is shown in FIGS. 13-15D. Theadhesive dispensing system 510 includes a contact nozzle 512 having adifferent configuration than the previously-described nozzles 19, 110,312, 412. For example, the contact nozzle 512 of this embodiment doesnot include an elongate adhesive chamber or a separate strand guide aspreviously shown in the other embodiments. These differences arehighlighted in further detail below.

With particular reference to FIG. 13, the nozzle 512 is coating one ormore stretched elastic strands 12 with a hot melt adhesive 14 so as toform an elasticized portion of a hygiene product such as a diaper orsanitary napkin. The nozzle 512 applies hot melt adhesive 14 onto theelastic strand 12 as the elastic strand 12 moves in a machine directionas indicated by arrows 16 in FIG. 13. The nozzle 512 then dischargespressurized air at the hot melt adhesive 14 as shown by arrows 18 tocause the hot melt adhesive 14 to spread around a periphery 20 of theelastic strand 12. The elastic strand 12 then continues in the machinedirection to first and second bonding reels 22 a, 22 b that couple firstand second nonwoven substrates 24 a, 24 b such as top and bottom sheetsof a typical diaper to the elastic strand 12 in a sandwich-likeconstruction. In this regard, the basic operation of the adhesivedispensing system 510 is similar to the general operation of thepreviously described embodiments.

The nozzle 512 is shown in further detail in FIGS. 14A through 15D. Thenozzle 512 is a V-notch nozzle 512 including a nozzle body 514 having anupper body portion 516 and a lower body portion 518. The nozzle body 514also includes a top side 520, a bottom side 522, a front side 524extending between the top and bottom sides 520, 522, and a rear side 526extending between the top and bottom sides 520, 522. The top side 520defines a mounting surface 520 configured to abut a module 15 when thenozzle 512 is coupled to the module 15. The upper body portion 516 isgenerally longer along the machine direction than the lower body portion518 from the front side 524 to the rear side 526, thereby giving thenozzle 512 a tapered appearance from the top side 520 to the bottom side522. Thus, the upper body portion 516 defines connection portions 528along the front side 524 and the rear side 526 for aligning the nozzle512 with the module 15. The nozzle 512 is clamped to the module 15 suchthat the top side 520 is coupled to the module 15 as well understoodfrom U.S. Pat. Nos. 6,676,038 and 7,559,487. In some embodiments, thenozzle body 514 may have a different shape and size, including but notlimited to being formed by stacked plates.

With reference to FIG. 14A, the nozzle 512 further includes an adhesiveinlet 530 and an air inlet 532 disposed along the mounting surface atthe top side 520 of the nozzle body 514. The adhesive inlet 530 issurrounded by a seal groove 534 that receives a seal member 536 betweenthe nozzle 512 and the previously-described module 15. The adhesiveinlet 530 is fluidically coupled to a plurality of adhesive passages 538formed in the nozzle body 514 and extending into the lower body portion518 of the nozzle body 514. Although two adhesive passages 538 are shownin FIG. 14B, more or fewer adhesive passages 538 may be coupled to theadhesive inlet 530 in other embodiments of the nozzle 512. Each adhesivepassage 538 is spaced from adjacent adhesive passages 538 in a lateraldirection transverse to the machine direction. Each adhesive passage 538delivers adhesive 14 from the adhesive inlet 530 to an adhesive orifice540 communicating with a respective slot in the form of a V-shaped notch542 (hereinafter V-notch 542) formed near the bottom side 522 of thenozzle body 514. The V-notch 542 operates inherently as a strand guidefor the nozzle 512 and replaces the strand guide and elongate adhesivechamber of the previous embodiments, although a separate expansionchamber is described in further detail below. These and other featuresof the V-notch 542 are described in further detail with reference toFIGS. 14C, 15A, and 15B below.

In a similar manner, the air inlet 532 is fluidically coupled to aplurality of air passages 544 formed in the nozzle body 514 andextending into the lower body portion 518. Each air passage 544 ispositioned proximate to and directly rearward of the respective adhesivepassage 538 within the nozzle body 514. In this regard, each set of oneadhesive passage 538 and one air passage 544 coats one strand 12 passingthrough the nozzle 512. As shown in FIG. 15A, it will be understood thatat least a lower portion of the adhesive passage 538 and the air passage544 are manufactured so as to be generally parallel to one another,thereby avoiding interferences between the air passages 538, 544 withinthe nozzle body 514. Each air passage 544 delivers air from the airinlet 532 to an air orifice 546 directed at the adhesive 14 in contactwith the strand 12. More particularly, the air orifice 546 is positionedadjacent to a rear surface 548, which is part of the rear side 526 ofthe nozzle body 514. As such, air discharged from the air passage 544and the air orifice 546 is directed along the rear surface 548 to act onthe adhesive 14 as the strand 12 exits the V-notch 542. As shown mostclearly in FIGS. 14C and 15D, the air orifice 546 is formed in anintermediate surface 550 extending from the rear surface 548. Thethicknesses 550 a and 550 b of the intermediate surface 550 on oppositesides of the air orifice 546 are minimized so as to reduce any eddycurrents that tend to form adjacent oblique surfaces surrounding the airorifice 546. The reduction of eddy currents along the intermediatesurface 550 makes the delivery of air toward the strand 12 more laminar.

With reference to FIGS. 14B and 14C, the V-notches 542 (e.g., slots 542)of the nozzle body 514 are shown in greater detail. In this regard, eachV-notch 542 is defined by two elongate converging surfaces 552 a, 552 bextending from an access slot 554 defined at the bottom side 522 of thenozzle body 514 to a top edge 556 where the converging surfaces 552 a,552 b intersect. Each of the converging surfaces 552 a, 552 b isgenerally planar such that the V-notch 542 defines a notch angle βbetween the converging surfaces 552 a, 552 b. The notch angle β isillustrated in this exemplary embodiment as about 90 degrees, althoughit will be understood that the notch angle β may alternatively be withina range of about 60 degrees to about 90 degrees in other embodimentsconsistent with the current invention. The access slot 554 communicateswith the V-notch 542 so that an elastic strand 12 can be insertedupwardly from below the nozzle body 514 into position within the V-notch542. More specifically, the elastic strand 12 is moved from the accessslot 554 into engagement with both converging surfaces 552 a, 552 badjacent the top edge 556. The top edge 556 is preferably formed so asto be dead sharp between the converging surfaces 552 a, 552 b, but itwill be understood that the top edge 556 may define a radius ofcurvature of up to 0.01 inches without departing from the scope of theinvention. As a result of the convergence of the surfaces 552 a, 552 band the sharp dimensioning of the top edge 556, the V-notch 542 definesa strand guide and no additional strand guide element is necessary toaccurately position the elastic strand 12 adjacent the top edge 556 whenthe elastic strand 12 is positioned within the V-notch 542.

Although no additional strand guide element is necessary with the nozzlebody 514 to position the elastic strand 12 within the V-notch 542, thenozzle 512 also includes a series of alignment pins 558 extendingdownwardly from the front side 524 of the nozzle body 514. The alignmentpins 558 are therefore located a small distance upstream from theV-notches 542 in a machine direction as previously described. Morespecifically, each V-notch 542 includes an inlet end 560 (FIG. 15A)bounded in opposing lateral directions by two of the alignment pins 558.When an elastic strand 12 is moved upwardly through the access slot 554,the elastic strand 12 is therefore also positioned between these twoalignment pins 558. The alignment pins 558 function to prevent “jumping”or unintentional movement of an elastic strand 12 from one V-notch 542to another V-notch 542. For example, an elastic strand 12 may include aknot tied between free ends of two supply reels of the elastic strand 12in order to enable continuous running of the elastic strand 12 throughthe nozzle 512. When such a knot encounters the inlet end 560 of theV-notch 542, the larger size of the knot may cause the elastic strand 12to “jump” temporarily away from the top edge 556 of the V-notch 542towards the access slot 554. This jump away from the V-notch 542 may besignificant enough to move the strand 12 below the access slot 554,which could hypothetically lead to re-entry of that strand 12 into adifferent adjacent access slot 554 and V-notch 542. However, thealignment pins 558 prevent such a jump into an adjacent access slot 554and V-notch 542 when such an event occurs. Although the alignment pins558 define a generally cylindrical shape in the illustrated embodimentto reduce any potential frictional contact with the elastic strands 12,it will be understood that differently shaped and sized alignment pins558 may be used in other embodiments. It will also be understood thatthe alignment pins 558 may be used to keep each elastic strand 12aligned with the respective V-notch 542 when a conventional lifting bar(not shown) is used to temporarily lift each of the elastic strands 12out of the V-notches 542, such as during breaks in operation of thenozzle 512.

Further features of the V-notch 542 and the nozzle body 514 are shown inFIGS. 15A and 15B, in which the elastic strand 12 and the adhesive 14are not shown to reveal additional elements. To this end, the V-notch542 extends from the inlet end 560 located at the front side 524 of thenozzle body 514 adjacent the alignment pins 558 to an outlet end 562located at the rear side 526 of the nozzle body 514. As described infurther detail below, the intersection of the V-notch 542 with this rearside 526 and the corresponding air flow at the rear side 526 encouragesrelease of adhesive material from the nozzle 512. Adjacent the inlet end560, the converging surfaces 552 a, 552 b include chamfered openingportions 564 that broaden the size of the opening into the V-notch 542,thereby reducing a likelihood of the elastic strand 12 running past asharp edge of the nozzle body 514. Over halfway along the length of theV-notch 542 (e.g., at a location closer to the outlet end 562 than theinlet end 560), the V-notch 542 is in fluid communication with theadhesive passage 538 via the adhesive orifice 540. As shown most clearlyin the bottom view of FIG. 15B, an expansion chamber 566 is formed byusing a ball-nose shaped mill to expand the size of the intersectionbetween the V-notch 542 and the adhesive orifice 540. The expansionchamber 566 includes a rounded profile and extends a small distanceabove the top edge 556 of the V-notch 542 such that the adhesive orifice540 defines a substantially planar outlet for adhesive material to flowinto the expansion chamber 566. As a result of the effects of die swellwithin the larger diameter expansion chamber 566, the adhesive 14 willinitially expand within the expansion chamber 566 and will be dischargedfrom the expansion chamber 566 into contact with the elastic strand 12and into the V-notch 542. The addition of the expansion chamber 566enables the use of a smaller diameter adhesive orifice 540, such as0.020 inches in the exemplary embodiment, which reduces the likelihoodof adhesive material dripping out of the adhesive orifice 540 betweendispensing cycles. In one example when a ball-nose shaped mill is usedto form the expansion chamber 566, the adhesive orifice 540 may define adiameter of about 0.020 inches while the expansion chamber 566 defines adiameter of about 0.050 inches to about 0.070 inches. It will beunderstood that the expansion chamber 566 may be formed by other knowncutting, drilling, and machining methods such as cutting scallop-shapedcutouts into the converging surfaces 552 a, 552 b in other embodimentsto modify the shape or size of the expansion chamber 566 withoutdeparting from the scope of the current invention. It will also beappreciated that the diameter of the adhesive orifice 540 may bemodified to adjust the velocity or flow of the adhesive 14 exiting theexpansion chamber 566 and spreading around the elastic strand 12 inother embodiments consistent with the current invention.

With reference to FIGS. 15C and 15D, the elastic strand 12 and adhesive14 are shown during operation of the nozzle 512. As described brieflyabove, the adhesive 14 is discharged from the adhesive passage 538through the adhesive orifice 540 and into the expansion chamber 566adjacent the top edge 556 of the V-notch 542. The expansion chamber 566is substantially filled with adhesive 14 such that the adhesive 14 flowsout of the expansion chamber 566 and into contact with the elasticstrand 12 passing the expansion chamber 566. More specifically, theadhesive 14 is applied to an upper surface 80 of the elastic strand 12at the expansion chamber 566, and the strand 12 effectively divides atleast a portion of the adhesive 14 flowing out of the expansion chamber566 to force the adhesive 14 to move along the converging surfaces 552a, 552 b of the V-notch 542 and begin spreading around the strand 12.The exemplary sharp dimensioning of the top edge 556 described in detailabove ensures that the strand 12 remains generally centered relative tothe expansion chamber 566, thereby ensuring the division and spreadingof the adhesive 14 flowing out of the expansion chamber 566. Because theelastic strand 12 passes the expansion chamber 566 at a greater velocitythan the adhesive 14 is supplied to the expansion chamber 566, thestrand 12 effectively draws the adhesive 14 from the expansion chamber566 in a semi-starved state and the adhesive 14 does not have anyopportunity to fly off the elastic strand 12. Immediately after exitingthe expansion chamber 566, the adhesive 14 along the upper surface 80 ofthe elastic strand 12 is moved mechanically by squeezing the adhesive 14between the converging surfaces 552 a, 552 b of the V-notch 542downstream of the expansion chamber 566. This mechanical movement causesspreading or wiping of the adhesive 14 around the periphery 20 of thestrand 12 (see, for example, FIG. 14C) as the strand 12 moves to theoutlet end 562 of the V-notch 542. The amount of initial spreading orwiping of the adhesive 14 around the periphery 20 may be adjusted byadjusting the notch angle β within the desired range of about 60 degreesto about 90 degrees. Consequently, when the elastic strand 12 reachesthe outlet end 562 of the V-notch 542, the adhesive 14 is alreadybeginning to spread and move around the periphery 20 of the strand 12.

As shown in FIG. 15D (and also in FIG. 14C), the rear surface 548 of thenozzle body 514 also intersects a lower rear surface 570 at an elongateedge 572. The outlet end 562 of the V-notch 542 intersects this lowerrear surface 570 such that the top edge 556 intersects the elongate edge572 at an adhesive release edge 572 a. The top edge 556 and the rearsurface 548 define an interior angle α at the adhesive release edge 572a. The interior angle α is an acute angle so that the adhesive releaseedge 572 a promotes sharp release of the adhesive 14 on the strand 12from the nozzle body 514. The interior angle α is measured in anupstream direction along the machine direction from the adhesive releaseedge 572 a. To this end, the interior angle α is defined by the nozzlebody 514 at the adhesive release edge 572 a. In the illustratedembodiment, the acute angle from the machine direction may be in therange of about 50 degrees to about 80 degrees. As the acute angle α ismade smaller within this range, the air flow from the air orifice 546becomes more parallel to the movement of the strand 12 along the machinedirection, which enables higher air pressures to be used for the airflow to further spread the adhesive 14 without blowing the adhesive 14off of the strand 12. The adhesive release edge 572 a therefore appliesa similar wiping or spreading effect on the adhesive 14 as theconverging surfaces 552 a, 552 b of the V-notch 542. Similarly, theacute angle α is also defined between the mounting surface at the topside 520 of the nozzle body 514 and a longitudinal axis 574 definedthrough the air orifice 546 and through at least a portion of the airpassage 544, as shown in FIG. 15A.

The air discharged from the air orifice 546 along the rear surface 548as shown by arrows 18 also assists with release of adhesive 14 from thenozzle body 514 at the adhesive release edge 572 a. The air travelingalong the rear surface 548 strikes the upper surface 80 of the strand 12at a non-perpendicular angle such that the formation of any eddycurrents around the adhesive release edge 572 a is believed to bediscouraged. More specifically, the air strikes the upper surface 80 ofthe strand 12 at the acute angle α described above. Therefore, theadhesive 14 remains attached to the moving strand 12 downstream of theadhesive release edge 572 a rather than building up on the nozzle body514. As a result, the risk of adhesive 14 building up on the nozzle body30, becoming charred, and blocking the air orifice 546 is substantiallyreduced or eliminated. The air discharged from the air orifice 546 alsocontinues to spread the adhesive 14 around the periphery 20 of thestrand 12 to thereby form varying thicknesses of adhesive 14 along thelength of the strand 12, as described in further detail below.

Upon release from the nozzle body 514, the adhesive 14 in contact withthe strand 12 is struck by additional air discharged from the airorifice 546 toward the elastic strand 12. The air causes the adhesive14, which is only partially spread around the periphery 20 of the strand12, to spread more around the periphery 20 of the strand 12 in order tocoat the strand 12 with the adhesive 14. It is believed that themechanical movement of the adhesive 14 with the converging surfaces 552a, 552 b immediately before this impact of the air further enhances thespreading effects caused by the air. The air discharged from the airorifice 546 does not blow the adhesive 14 off of the strand 12 becausethe adhesive 14 is applied to the strand 12 and begins forming anadhesive bond with the strand 12 within the V-notch 542 prior to beingstruck with the air. As a result, the adhesive 14 coats substantiallythe entire periphery 20 of the strand 12 as explained below.

The adhesive 14 forms a coating on the strand 12 that appears continuousto the naked eye, but it is believed that this coating is not entirelycontinuous along the length of the strand 12. As described above, theadhesive 14 is extruded from the adhesive orifice 540 into the expansionchamber 566 and then onto the strand 12. Consequently, the adhesive 14contacts the moving strand 12 and rapidly accelerates, which causes theadhesive 14 to be applied to the strand 12 in a semi-starved state suchthat the amount of adhesive 14 varies along the length of the strand 12.More particularly, the adhesive 14 is believed to form localized massesor thicker sections separated by thinner sections as the adhesive 14 isaccelerated by the elastic strand 12. These localized masses of adhesive14 are configured to become discrete bond points when securing theelastic strand 12 to nonwoven substrates. Then the adhesive 14 is struckwith air from the air orifice 546, which causes additional spreading ofthe adhesive 14 that tends to further spread the adhesive 14 intolocalized masses.

As a result of these operational steps, the resultant coating formed onthe strand 12 is believed to include thickness irregularities along thelength of the strand 12. In this regard, FIGS. 15C and 15D schematicallyillustrate that the adhesive 14 forms a coating with a plurality ofthicker portions 84 a, a plurality of thinner portions 84 b, andpreferably a plurality of void portions 84 c where no adhesive 14 is onthe strand 12. These portions 84 a, 84 b, 84 c are shown as an artist'srendering and it will be appreciated that the actual appearance anddistribution of these portions 84 a, 84 b, 84 c may vary in actual usedepending on operation parameters such as air pressure. The repeatablecontinuous appearance to the naked eye of the adhesive 14 on the strand12 is desirable in hygiene products, but the thickness irregularities ofthe coating believed to be formed by the adhesive 14 advantageouslyresults in the thicker portions 84 a functioning as discrete bond pointsformed along the length of the strand 12 when adhered to one or more ofthe substrates 24 a, 24 b, as described in detail above. Morespecifically, when bonded between two nonwoven substrates 24 a, 24 b,the coated elastic strand 12 is coated with sufficient adhesive 14 toexhibit a high level of creep resistance and, by virtue of the discretebond point effect, also exhibits a high level of force retraction.

Consequently, the adhesive dispensing system 510 of this embodimentoperates in a general manner similarly as the nozzles 19, 110, 312, 412previously described. More specifically, the adhesive dispensing system510 applies adhesive 14 by contact coating the adhesive 14 onto a movingelastic strand 12 and then spreads the adhesive 14 using air flow afterthe adhesive 14 is in contact with the strand 12. The adhesivedispensing system 510 can advantageously coat a strand 12 with adhesive14 with low adhesive 14 consumption and a low adhesive viscosity, ifdesired. It will be understood that the adhesive dispensing system 510of this embodiment is operable to coat stretched elastic strands 12moving faster and spaced closer than with conventional non-contactnozzle designs because the adhesive 14 is placed into direct contactwith the strands 12 and because the pressurized air flow does notrequire significant spacing to avoid air flow interference from onestrand 12 to another strand 12. Therefore, the adhesive dispensingsystem 510 improves the hygiene product assembly process.

The present invention also includes a method of contact coating astretched elastic strand with an adhesive, where the strand includes aperiphery with an upper surface. The method includes moving the strandin a machine direction relative to a contact nozzle, discharging theadhesive from the contact nozzle onto the upper surface of the strand asthe strand moves, and discharging pressurized air at the adhesive on themoving strand. The air causes the adhesive to spread around theperiphery of the strand to thereby coat the strand with the adhesive.The air also assists with release of the adhesive from the contactnozzle and cleans the contact nozzle from collecting adhesive build-upthat would eventually char and adversely affect the operation of thecontact nozzle. Thus, the method of coating the strand enables coatingof a strand without the need to produce a spiraling pattern or otherpattern with process air impacting a dispensed adhesive filament duringflight.

The discharge of the air is controlled to have various air flowcharacteristics depending on the type of coating desired on the strand.In one example, the air is discharged continuously at the adhesive incontact with the strand as the strand moves to cause generallycontinuous spreading of the adhesive around the strand. In anotherexample, the air is discharged in a non-continuous manner such as inperiodic pulses at the adhesive in contact with the strand as the strandmoves to cause a non-continuous (e.g., pulsed) spreading of the adhesivearound the strand. The air is discharged at an acute angle relative tothe machine direction as measured between the direction of air dischargeand the elastic strand upstream of the air. This acute angle may also bemeasured between a longitudinal axis through an adhesive orifice and amounting surface of the contact nozzle, the mounting surface configuredto be coupled to a module and including an adhesive inlet for receivingthe adhesive from the module. In the illustrated embodiment, the acuteangle from the machine direction may be in the range of about 50 degreesto about 80 degrees, which is believed to discourage the formation ofany eddy currents in the air that could cause the adhesive to blow offthe strand.

In one alternative, multiple streams of air are discharged toward theadhesive on the strand to cause the adhesive to spread around oppositesides of the periphery of the strand. The multiple streams of air arestaggered in the machine direction such that the multiple streams of airstrike the strand at different locations along the machine direction.Alternatively, the multiple streams of air are aligned in a planeperpendicular to the machine direction such that the multiple streams ofair strike the strand at about the same location along the machinedirection. It will be understood that each of the multiple streams ofair in these embodiments continues to be discharged at an acute anglefrom the machine direction.

In some embodiments, moving the strand includes moving the strandthrough a strand guide and through an elongate adhesive chamber. Inthese embodiments, dispensing the adhesive onto the upper surface of thestrand further includes filling the adhesive chamber of the contactnozzle with the adhesive as the strand moves through the adhesivechamber. The strand is positioned within the adhesive chamber to forceinitial spreading of the adhesive around the periphery of the strandwithin the adhesive chamber. Furthermore, the movement of the stranddraws the adhesive out of the adhesive chamber. The strand is moved at avelocity greater than the velocity at which the adhesive enters theadhesive chamber so that a minimum amount of adhesive is applied to thestrand. In some arrangements, the strand is angled with respect to theadhesive chamber or the adhesive chamber is tapered such that theadhesive is located in the adhesive chamber for a longer period of time,thereby causing increased spreading of adhesive around the strand. Inthese arrangements, the strand is effectively moved laterally within theadhesive chamber as the strand travels along the length of the adhesivechamber, which further encourages the increased spreading of adhesivearound the strand. In other embodiments, the adhesive is dispensed ontothe upper surface of the strand from an adhesive orifice communicatingwith a V-notch through which the strand is moving. In these embodiments,the surfaces defining the V-notch mechanically move the adhesive andbegin spreading the adhesive around the periphery of the strand. As aresult of the spreading of the adhesive both within the adhesive chamberor V-notch and caused by air flow directed at an acute angle to theelastic strand (e.g., angled at about 50 degrees to about 80 degrees)outside the adhesive chamber or V-notch, the coating of adhesive on thestrand is believed to include random thickness irregularities thatfunction as discrete bond points formed along the length of the strand.

In one example, the method of coating a strand is used during anassembly process for a hygiene product. In these embodiments, the methodfurther includes bonding the stretched elastic strand between twononwoven substrate layers after the hot melt adhesive has been spreadaround the periphery of the strand to form at least a portion of thehygiene product. Depending on the needs of the user, the hot meltadhesive is spread using an air flow in a continuous manner or a pulsedmanner. The method therefore advantageously coats a strand with adhesivewith low adhesive consumption and a low adhesive viscosity. As a result,the method of the present invention improves the hygiene productassembly process.

In another example, the method of coating a strand is used to coatmultiple stretched elastic strands simultaneously. To this end, thecontact nozzle may include duplicated structure that enables thedischarge of adhesive and pressurized air onto each of a plurality ofstrands. The coated elastic strands may then be used to assemble one ormore hygiene products. It will be understood that the method accordingto any of the embodiments described above may be used to coat multiplestrands.

While the present invention has been illustrated by the description ofspecific embodiments thereof, and while the embodiments have beendescribed in considerable detail, it is not intended to restrict or inany way limit the scope of the appended claims to such detail. Thevarious features discussed herein may be used alone or in anycombination. Additional advantages and modifications will readily appearto those skilled in the art. For example, the slots shown in the nozzlebodies of the various embodiments may be modified in shape, size, andconfiguration without departing from the scope of the current invention.The invention in its broader aspects is therefore not limited to thespecific details, representative apparatus and methods and illustrativeexamples shown and described. Accordingly, departures may be made fromsuch details without departing from the scope or spirit of the generalinventive concept.

What is claimed is:
 1. A method of contact coating at least one elasticstrand with an adhesive, a first strand having a periphery with an uppersurface, the method comprising: moving the first strand through anadhesive chamber in a machine direction relative to a contact nozzle;spreading the adhesive in the adhesive chamber into contact with theupper surface of the first strand; and discharging pressurized air atthe adhesive on the first strand to cause the adhesive to spread aroundthe periphery of the first strand without blowing adhesive off the firststrand.
 2. The method of claim 1, wherein discharging the pressurizedair at the adhesive on the first strand comprises discharging thepressurized air at an acute angle, the acute angle being measuredbetween the direction of discharge of the pressurized air and the uppersurface of the first strand upstream of the pressurized air in themachine direction.
 3. The method of claim 1, wherein discharging thepressurized air at the adhesive on the first strand comprisesdischarging multiple streams of pressurized air at the adhesive on thefirst strand to cause the adhesive to spread around opposite sides of aperiphery of the first strand without blowing the adhesive off the firststrand.
 4. The method of claim 3, wherein discharging the multiplestreams of pressurized air at the adhesive on the first strand comprisesdischarging the multiple streams of pressurized air at staggeredlocations along the machine direction such that the multiple streams ofpressurized air strike the first strand at different locations along themachine direction.
 5. The method of claim 3, wherein discharging themultiple streams of pressurized air at the adhesive on the first strandcomprises discharging the multiple streams of pressurized air aligned ina plane perpendicular to the machine direction such that the multiplestreams of pressurized air strike the first strand at about the samelocation along the machine direction.
 6. The method of claim 1, whereindischarging the pressurized air at the adhesive on the first strandcauses cleaning of the contact nozzle and discouraging of accumulationof adhesive build-up on the contact nozzle.
 7. The method of claim 1,wherein discharging the pressurized air at the adhesive on the firststrand causes assistance with release of the adhesive from the contactnozzle.
 8. The method of claim 1, wherein discharging the pressurizedair at the adhesive on the first strand comprises discharging thepressurized air continuously at the adhesive on the first strand tocause the adhesive to substantially continuously spread around theperiphery of the first strand.
 9. The method of claim 1, whereindischarging the pressurized air at the adhesive on the first strandcomprises discharging the pressurized air non-continuously at theadhesive on the first strand to cause the adhesive to non-continuouslyspread around the periphery of the first strand.
 10. The method of claim1, wherein discharging the pressurized air at the adhesive on the firststrand causes the adhesive to spread around the periphery of the firststrand such that the adhesive defines thickness irregularities along thefirst strand, the thickness irregularities including thicker adhesiveportions and thinner adhesive portions.
 11. The method of claim 10,wherein the thickness irregularities include void portions that containno adhesive on the first strand.
 12. The method of claim 1, wherein asecond strand includes a periphery with an upper surface, and the methodfurther comprises: moving the second strand through another adhesivechamber in the machine direction relative to the contact nozzle;spreading the adhesive in the adhesive chamber onto the upper surface ofthe second strand; and discharging pressurized air at the adhesive onthe second strand to cause the adhesive to spread around the peripheryof the second strand without blowing adhesive off the second strand. 13.The method of claim 12, wherein: the adhesive is simultaneouslydischarged onto the first strand and the second strand; and thepressurized air is simultaneously discharged onto the first strand andthe second strand.
 14. The method of claim 1, moving the first strandthrough the adhesive chamber in the machine direction comprises movingthe first strand through the adhesive chamber at a first velocitygreater than a second velocity at which the adhesive enters the adhesivechamber.
 15. A method of contact coating at least one elastic strandwith an adhesive, a first strand having a periphery with an uppersurface, the method comprising: moving the first strand in a machinedirection relative to a contact nozzle; discharging the adhesive fromthe contact nozzle into contact with the upper surface of the firststrand; and discharging pressurized air non-continuously at the adhesiveon the first strand to cause the adhesive to non-continuously spreadaround the periphery of the first strand without blowing adhesive offthe first strand.
 16. The method of claim 15, wherein discharging thepressurized air non-continuously at the adhesive on the first strandcauses the adhesive to spread non-continuously around the periphery ofthe first strand such that the adhesive defines thickness irregularitiesalong the first strand, the thickness irregularities including thickeradhesive portions and thinner adhesive portions.
 17. The method of claim16, wherein the thickness irregularities include void portions thatcontain no adhesive on the first strand.
 18. The method of claim 15,wherein a second strand includes a periphery with an upper surface, andthe method further comprises: moving the second strand in the machinedirection relative to the contact nozzle; discharging the adhesive fromthe contact nozzle onto the upper surface of the second strand; anddischarging pressurized air non-continuously at the adhesive on thesecond strand to cause the adhesive to non-continuously spread aroundthe periphery of the second strand without blowing adhesive off thesecond strand.
 19. The method of claim 18, wherein: the adhesive issimultaneously discharged onto the first strand and the second strand;and the pressurized air is simultaneously discharged onto the firststrand and the second strand.
 20. A method of contact coating at leastone elastic strand with an adhesive, a first strand having a peripherywith an upper surface, the method comprising: moving the first strand ina machine direction relative to a contact nozzle; discharging theadhesive from the contact nozzle into contact with the upper surface ofthe first strand; and discharging multiple streams of pressurized air atthe adhesive on the first strand at staggered locations along themachine direction such that the multiple streams of pressurized airstrike the first strand at different locations along the machinedirection to cause the adhesive to spread around opposite sides of theperiphery of the first strand without blowing the adhesive off the firststrand.